Jensens Device

An early use of CallByName, see the following AlgolLanguage code:

   begin integer i;

      real procedure sum(i, lo, hi, term);
           value lo, hi; integer i, lo, hi; real term;
           comment term is passed by-name;
      begin real temp; temp := 0;
            for i := lo step 1 until hi do
               temp := temp + term;
            sum := temp
      end;

      print( sum(i, 1, 100, 1/i), 6, 3 )
   end

The answer is 5.187378...

Apparently DonaldKnuth thought it was a good idea, and wrote the ManOrBoy test to determine which compilers could handle it correctly.